diff --git a/src/gb/gprs_ns2.c b/src/gb/gprs_ns2.c
index 4d27333..3574f28 100644
--- a/src/gb/gprs_ns2.c
+++ b/src/gb/gprs_ns2.c
@@ -1422,6 +1422,9 @@
 	OSMO_ASSERT(nse);
 
 	llist_for_each_entry(nsvc, &nse->nsvc, list) {
+		/* A pre-configured endpoint shall not be used for NSE data or signalling traffic
+		 * (with the exception of Size and Configuration procedures) unless it is
+		 * configured by the SGSN using the auto-configuration procedures */
 		if (nsvc->sns_only)
 			continue;
 
diff --git a/src/gb/gprs_ns2_internal.h b/src/gb/gprs_ns2_internal.h
index 29717c6..b4d0a0d 100644
--- a/src/gb/gprs_ns2_internal.h
+++ b/src/gb/gprs_ns2_internal.h
@@ -220,6 +220,7 @@
 	void *priv;
 
 	bool nsvci_is_valid;
+	/*! should this NS-VC only be used for SNS-SIZE and SNS-CONFIG? */
 	bool sns_only;
 
 	struct rate_ctr_group *ctrg;
diff --git a/src/gb/gprs_ns2_sns.c b/src/gb/gprs_ns2_sns.c
index 11c5a8e..51e4e9e 100644
--- a/src/gb/gprs_ns2_sns.c
+++ b/src/gb/gprs_ns2_sns.c
@@ -914,6 +914,9 @@
 		gss->sns_nsvc = ns2_ip_bind_connect(bind, gss->nse, remote);
 		if (!gss->sns_nsvc)
 			return;
+		/* A pre-configured endpoint shall not be used for NSE data or signalling traffic
+		 * (with the exception of Size and Configuration procedures) unless it is configured
+		 * by the SGSN using the auto-configuration procedures */
 		gss->sns_nsvc->sns_only = true;
 	}